This invention relates to a combination finger joint cutter head mounted on a rotatable shaper spindle such that the cutter head cuts finger joints and trims the joints in a piece of wood. Cooperating finger joint cuts may be made such that pieces of wood or other material may be joined together. Finger joint cutting is an economical process to produce a long piece of wood from a number of short pieces of wood by providing matching or cooperating surfaces at the ends of the wooden pieces that can be fitted together and then glued.
Present processes for profiling the ends of wood pieces are disclosed in U.S. Pat. No. 3,807,096, issued Apr. 30, 1974, wherein the apparatus disclosed produces matching finger joints by means of a pair of opposing abrasive profiling cutters that alternately cut from the edge to the center at the ends of the wood. The apparatus includes a wood positioning device so that the profile cutters need not be relocated for subsequent cuts. The depth of the cut is limited by the tool profile.
More recently the industry has developed a deeper tooth finger joint of a trapezoidal shape that is cut using a stack of cutter blades and interposing spacers between the blades as needed, to obtain the deeper cut fingers. Such cutter blade heads do not trim the ends of the wood fingers-a separate knife cutting blade head or saw must be used for end trimming. Because the end cutting and finger joint cutting are separate processes, the possibility of improper end trimming relative to finger joint cutting is increased.
Finger jointing requires extremely precise cutting of the trapezoidal tooth profiles in order to properly mate the fingers of one piece of the cavity portions of a mated piece. Improper cutting results in a poor fit, which forms a piece having decreased joint strength after mating and gluing. It is important that the depth of the tooth be such that the tips of the mating teeth do not bottom out in the mating cavity since this would result in gaps along the sides of each tooth and consequent poor bonding. Conversely, if the tooth is cut too short, a gap at the tip of each tooth results, again reducing the bonding strength. Thus it can be seen that consistent and precise end trimming is an important step in the finger jointing process.
Adjustment of prior art finger joint trim knives is difficult to accomplish with any degree of certainty as to the amount of adjustment effected.
It is the purpose of this invention to provide a finger joint cutter head with an easy, vernier adjustment mechanism permitting contraction and extention of straight trim knives simultaneously with a single adjustment. More substantial adjustment of the finger joint cut depths requires removal of a cutter head top plate and cutter blades to interpose the spacers between the blades. Such mechanism permits adjustment more quickly and accurately than possible with prior art devices, resulting in a more precise finger joint cut. In a preferred embodiment, vernier adjustment of the device can be made while the finger joint cutter head is mounted on the spindle.